I wasn't sure about whether to purchase this game having played the demo; I found myself getting bored after a few playthroughs. However, in the end I did and am very happy.
The story is gripping and the characters fascinating. It is all told out in fantastic graphic cut scenes, and I never lost interest.
The gameplay is also solid. Every building in the gameworld is scalable and pretty soon Cole is able to "ride" rails and wires around the city. His electrical, upgradeable powers are awesome and destructive and there is a variety of enemies on which to unleash them. There is also a stunts list and stunt trophies, as well as collectible blast shards and dead drops which add plenty of playability and replayability.
Another major part of the game is the karma system. Several of the missions (of which there are plenty) cause you to make moral choices which are fun and intriguing. Your karma has a fair impact on the city and Cole; if you're good (heroic), then the city is bright and relatively cheerful, the skies blue, and Cole looks normal (with blue electricity); infamous, then the skies turn dark, and the city falls into further disrepair. Cole becomes sinister and looks corrupted His electricity turns red.
However, if you choose to play the story twice (which I highly recommend), you will notice that your karma really has no significant effect on its outcome, nor in its buildup, although it does slightly change Cole's powers.
Also, the graphics are perhaps not what they should be; they just aren't that great, and neither is the draw distance.
Nonetheless, do not allow this to detract from an excellent gaming experience. Infamous' combination of platforming and role-playing is striking and never dull, while the city feels alive and responds to your actions. The karma system adds a whole lot of replayability, and the trophy list is perfectly balanced; each one is "getable". Overall, this is one of the best PS3 exclusives, and indeed one of the best games on the market. This is a must-buy.